The long term goals of this project are to understand the bases of the interactions between Schwann cells and axons. These include the mechanism of recognition, adhesion and, in particular, the process of differentiation with respect to synthesis of components of basal lamina and myelin. The immediate aims are to isolate purified populations of Schwann cells from rat sciatic nerve by use of antimitotic agents as well as immunological selection and to maintain them in culture. For studying the role of individual components in differentiation, a defined serum-free medium will be developed and optimized for the culture of secondary Schwann cells. Modifications of this medium will be evaluated for selective growth of primary Schwann cells thus avoiding the use of antimitotic agents. Agents that are known to induce differentiation in vivo, such as basal lamina and neuronal components will be examined for their effects on expression of Schwann cell differentiation. Finally, the early events in the regulation of synthesis of myelin specific proteins will be examined. These include rates of transcription, stability of the specific mRNA, rates of translation, and the appearance of myelin specific lipids and proteins. These studies will be conducted by standard immunofluorescence, biochemical and molecular biological techniques. Having cDNA probes to P0, P1, and P2 makes these studies feasible. Transfection of Schwann cells is also planned. Although not a prerequisite for these studies, these cells will aid future investigations on differentiation as well as permitting investigators to obtain Schwann cells from small quantities of tissue. Understanding the early events in myelinogenesis should provide insight into normal development and the pathophysiology of demyelinating diseases as well as repair by remyelination. In the latter instance, this has implications for therapeutic intervention in demyelinating disease, such as peripheral neuropathies. Since the axonal signal for adhesion of oligodendrocytes is similar to that of Schwann cells, information obtained may be extrapolated to the Central Nervous System.